The present invention relates to a heating tank which heats a target to be heated stored by a circulated refrigerant of a heat pump in the tank, and a hot water storage tank.
Heretofore, in this type of heating tank, for example, a hot water storage tank in which hot water is stored, water (a target to be heated) has been heated by a circulated refrigerant of a heat pump to produce the high-temperature hot water. The hot water is stored in the hot water storage tank, and the hot water stored in the hot water storage tank is taken out, if necessary. Specifically, the hot water storage tank is connected to a heat exchanger via a pipe, and the hot water produced via the heat exchanger is stored in the hot water storage tank.
However, in a case where the hot water produced via the heat exchanger is stored in the hot water storage tank in this manner, a pump for feeding water is required for circulating the water through the heat exchanger, and there has occurred a problem that a device cost and a power consumption increase. Furthermore, since the high-temperature hot water produced by the heat exchanger returns to the hot water storage tank via the pipe, reliability of a component such as the pipe needs to be sufficiently considered, and there are many problems that the temperature of the hot water drops in a process of passing the hot water through the pipe, to result in heat loss and the like.
To solve the problem, there has been developed a device in which the heat exchanger is incorporated in the hot water storage tank, or a refrigerant pipe of the heat exchanger is wound around a wall surface of the hot water storage tank, to directly heat the water in the hot water storage tank by the circulated refrigerant of the heat pump, for example, a device in which a so-called heat release section of the heat pump is provided integrally in the hot water storage tank (e.g., see Japanese Patent Application Laid-Open No. 2001-221500).
However, as in the former case, when the pipe where the refrigerant of the heat exchanger flows is incorporated in the hot water storage tank, the above problem of the heat release loss can be solved, but the refrigerant pipe needs to be provided in the hot water storage tank. When the pipe is cracked or broken, the water in the hot water storage tank is polluted, and there have been many problems of safety and reliability.
On the other hand, as in the latter case, when the refrigerant pipe of the heat exchanger is wound around the wall surface of the hot water storage tank, heat of the refrigerant is conducted to the water in the tank via the pipe and the wall surface, and this lowers heat conductivity. Moreover, since a contact area between the pipe and the wall is very small, an even thermally conductive surface cannot be secured, and efficiency deteriorates.